There are many ways to coat objects. The art of coating, often referred to as painting, uses various tools to coat surfaces including brushes, rollers, sprayers, foam brushes, etc. In general, many things are coated with various materials such as paint, varnish, polyurethane, stain, etc.
Often, it is desired to coat a surface with a smooth coating of a material such as paint. Much attention is taken to apply a smooth coat of paint or other coatings. People who apply coatings (e.g. painters), work hard to apply clean, even coats; painting in specific patterns, using high-quality brushes and rollers, etc. No matter how hard such people work at applying clean and even coats, impurities often hamper such efforts. Paint impurities come from many sources. Old paint often congeals or fragmented pieces of dried paint often find their way into the paint and onto the paint applicator. Other sources of such contamination come from the environment, dust, hair, animal hair, dirt, soil, grass, insects, etc. When such contamination mixes into the paint and winds up on the applicator (e.g., brush, roller, etc.), the contamination eventually winds up on the target that is being coated (e.g., wall). The contamination causes uneven coating on surfaces, smearing, bumps, and other marring of a quality coating.
When painting with a roller, contamination on the roller often transfers to the surface being coated or remains on the roller; causing uneven coating when the contamination contacts the surface. Applying a layer of paint on an outside wall near the grass or dirt is almost impossible, as pieces of grass or dirt almost always wind up on the roller. Once the contamination finds its way onto the roller, the contamination often remains on the roller, or is transferred to the surface being coated. The person applying the paint often uses a finger or rag to remove the contamination, piece by piece, but such is messy and time consuming.
For commercial painters, often an inspection is made by an inspector or project manager and, should any debris be found on a painted surface, the commercial painter is often required to sand to remove the debris and repaint the entire surface.
What is needed is a system that will systematically remove impurities from liquid coating material when using a paint roller.